In the construction of large commercial buildings such as parking structures and the like, the basic construction unit comprises pre-stressed concrete beams which may extend for fifty or sixty feet in length. Such beams are generally produced at the construction site and towards this end, there is initially provided a casting bed installation for forming the beams. The casting bed itself may extend for several hundred feet within large massive earth anchors at opposite ends of the bed for holding pre-tensioning wires utilized in providing the pre-stressed concrete beams. By providing an elongated casting bed of length constituting a multiple of the length of the beams, the pre-tensioning wires need only be pre-tensioned once preparatory to pouring concrete in the casting bed there being provided end to end divider forms periodically along the casting bed through which the pre-tensioning wires pass. After casting, the beams can be separated at the end forms.
Resistance to the pre-stressing forces resulting from pre-tensioning the wires preparatory to casting, as stated, requires massive abutments or anchors buried in the ground. Not only is such construction of the casting facility expensive, but the same is necessarily of a fixed length and thus production units must be fitted into the fixed distance between abutments. Moreover, the facilities must be demolished if they are to be removed.